Fewer will go back to the Intel 8008 or even 4004 era which were the first integrated circuit chips commercially ... the era of programmable vacuum tube machines. [Mike] has gone back to the ...

circuits [David] has already built vacuum tube versions of. The only part left was the discharge transistor; a pentode was enlisted to stand in for that vital function, making the circuit complete.

A vacuum tube is just that: a glass tube surrounding a vacuum (an area from which all gases have been removed). What makes it interesting is that when electrical contacts are put on the ends ...

it really is a crazy tube circuit featuring an actual vacuum tube under the hood. The BK Butler came as a rack-mounted unit and as a pedal, and was famously played by the likes of Eric Johnson ...